Treatment of fuel oil with an alkyl pyrrole



United States Patent TREATMENT OF FUEL OIL WITH AN ALKYL PYRROLE William T. Robinson, Hollywood, 111., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware No Drawing. Application August 25, 1951, Serial No. 243,743

7 3 Claims. (Cl. 196-23) This application relates to a novel method of treating fuel oil in order to improve its stability properties.

At the present time fuel oils come primarily from nondestructive distillation of oil, commonly referred to in the art as straight run distillates, and from catalytic and noncatalytic cracking processes, commonly referred to in the art as cycle stocks. The term cycle stocks" is used because the fuel oils separated from the fraction which is recycled to the cracking process for further conversion therein. Other sources of fuel oil may include those produced by the reaction of carbon monoxide with hydrogen in the process known as the Fischer-Tropsch process, etc. Regardless of the source, fuel oils, particularly when comprising blends of two or more different oils, tend to undergo discoloration and form sediment in storage, and the present invention is directed to a novel method of treating fuel oils.

The formation of sediment in fuel oil is objectionable because the sediment tends to plug strainers, burner tips, injectors, etc., and, when used as diesel fuel, tends to plug injectors, valves, filters, etc. The sediment referred to herein is different from the solid material originally contained in fuel oil and referred to in the art as B. S. 8: W. The sediment with which the present invention is concerned is not contained as such in the fuel oil as produced but forms during storage.

Discoloration of fuel oil is also undesirable because many fuel oils are marketed under a color specification, and discolored fuel oil in most cases cannot meet the color specification. As will be hereinafter set forth, treatment of the fuel oil in accordance with the novel method of the present invention will serve to avoid discoloration of fuel oil, as well as avoiding sediment formation in storage.

The term fuel oil is used in the present application in a generic sense to include hydrocarbon distillates heavier than gasoline. These hydrocarbon distillates are marketed under various trade names such as fuel oil, furnace oil, heater oil, burner oil, diesel oil, jet fuel, etc. As hereinbefore set forth, in the past the fuel oils have come mostly from straight run distillates, but with the increasing amount of catalytic cracking processes being installed, a considerable quantity of catalytic cycle stock is available and is being used for fuel oil. However, catalytic cycle stock generally is not of satisfactory burner qualities and cannot be used alone. Refiners, therefore, have adopted the practice of blending catalytic cycle stock with straight run distillate to produce a salable fuel oil and, as hereinbefore set forth, these-blended oils tend to undergo discoloration and sediment formation to a greater extent.

Although the present invention is particularly applicable to the treatment of blends of catalytic cycle stocks and straight run distillates, there are cases where the straight run distillate or the catalytic cycle stock will undergo excessive discoloration and sediment formation in storage. It is understood that the present process may be used for eliminating this deterioration. Similarly, the present invention may have application to the treatment of lubrieating oil, transformer oil, turbine oil, etc. which undergo excessive deterioration in storage.

In one embodiment the present invention relates to a process for treating fuel oil which comprises adding to the fuel oil a compound which promotes sediment formation, and thereafter treating the fuel oil to remove the sediment and to produce a fuel oil of improved properties.

In a specific embodiment the present invention relates to a process for treating fuel oil which comprises adding to the fuel oil a small amount of a pyrrole compound which promotes sediment formation, and thereafter filtering the fuel oil to remove the sediment and to produce a fuel oil of improved properties.

In accordance with the present invention a compound is added to the fuel oil which promotes sediment formation. In this manner the components of the fuel oil which form sediment in storage are seeded and thereby precipitate out as sediment at a much faster rate than would otherwise occur. This permits removal of the undesirable components of the fuel oil while still under control of the refiner and avoids deterioration subsequently. These components which form sediment also are responsible for discoloration of the fuel oil and, by accelerating precipitation of these components and the removal thereof from the fuel oil, the filtered fuel oil will be more stable both in regards to sediment formation and discoloration.

Any suitable compound may be used to promote sediment formation. Particularly suitable compounds include heterocyclic nitrogen compounds and more specifically pyrrole compounds including pyrrole, alkylated pyrroles,

including methyl pyrrole, ethyl pyrrole, propyl pyrrole,

butyl pyrrole, etc., dialkyl pyrroles including 2,5-dimethyl pyrrole, 2,5-diethyl pyrrole, 2,5-dibutyl pyrrole, 2,5-dipropyl pyrrole, etc., pyrazole compounds including pyrazole, alkylated pyrazoles, including 3-methyl pyrazole, 3-ethyl pyrazole, 3-propyl pyrazole, 3-butyl pyrazole, etc., 3,5-dimethyl pyrazole, 3,5-diethyl pyrazole, 3,5-dipropyl pyrazole, 3,5-dibutyl pyrazole, etc., 3-methyl- S-ethyl pyrazole, 3-methyl-5-propyl pyrazole, 3-ethyl-5- propyl pyrazole, 3-propyl-5-butyl pyrazole, etc., indole, alkylated indoles, quinoline, alkylated quinolines, isoquinolines, carbazole, alkylated carbazole, etc.

Other suitable but not necessarily equivalent compounds include heterocyclic sulfur compounds including thiophenols, alkylated thiophenols, thiophene, alkylated thiophenes, tertiary alkyl mercaptans including particularly tertiary butyl mercaptan, tertiary amyl mercaptan, etc., alkyl polysulfides including isopropyl disulfide, tertiary butyl disulfide, tertiary amyl disulfide, tertiary hexyl disulfide, tertiary heptyl disulfide, tertiary octyl disulfide, etc. As hereinbefore set forth, it is understood that any suitable compound which promotes sediment formation in the fuel oil may be employed within the scope of the present invention, with the understanding that these various compounds are not necessarily equivalent.

The amount of promoting compound to be employed in accordance with the present invention will vary with theparticular fuel oil being treated and the specific compound employed. However, as a general rule, the promoting compound will be used in a concentration not above about 5% by weight of the fuel oil and preferably within the range of from about 0.001% to about 1% by weight.

In order to reduce the time that the fuel oil is to be kept in storage in order to allow sediment formation to occur, it is particularly preferred to add a precipitating agent in order to hasten formation of the sediment. Any suitable precipitating agent may be employed. For example, in the case of 2,5-dimethyl pyrrole, mercuric chloride may be added to the fuel oil to precipitate sediment formation.

It is understood that other suitable means of accelerating sediment formation may be employed within the scope of the present invention. For example, the fuel oil containing the promoting compound, with or without the precipitating agent, may be heated to EIH-CIQVHtQd tempera-= ture in order to further promote sediment formation. The

elevated temperature generally will not be above about 600 F. and, in most cases, may be within the range of from about 125" to about 300 F.

The promoting compound may be incorporated in the fuel oil in any suitable manner. In general it is preterred to agitate the fuel oil mixture after addition of the promoting compound and precipitating agent, when the 'latter is employed, in order to insure intimate mixing of these added materials with thecomponents in the fuel oil which are to be removed as sediment. Any conventional means of effecting this intimate mixing may. be employed.

After sediment formation has occur-red, the fuel oil is treated to remove the sediment and to leave a fuel oil of improved stability properties. Any suitable method for removing the sediment may be employed. A particularly preferred method is to filter the fuel oil in any suitable filtering equipment which will satisfactorily remove the sediment and precipitate.

The following example is introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

Example I A substantially stable Coastal fuel oil blend comprising 50% catalytic cycle stock and 50% straight run distillate may be treated in accordance with the present invention. The additive to be employed comprises '2,5-dim'ethyl pyrrole which may be added in a nitrogen concentration of 0.1% by weight. When stored at an elevated temperature, a control sample of the fuel oil not containing the additive will form a small amount of sediment. Upon the addition of the 0.1% nitrogen as 2,5-dimethyl pyrrole, another sample of the fuel oil, after similar storage, will form a considerably greater amount of sediment.

It is apparent that the addition of 2,5-dimethyl pyrrole will serve to increase sediment formation. In accordance with the present invention the sediment is removed by filtering the fuel oil and thereby will leave a fuel oil of reduced sediment formation and discoloration in subsequent storage.

I claim as my invention:

1. A process for treating fuel oil which comprises adding to the fuel oil from about 0.001% to about 1% by weight of 2,5-dimethyl pyrrole, subsequently adding thereto mercuric chloride to precipitate sediment formation, and thereafter filtering the fuel oil to remove thcscdiment and to produce a fuel oil of improved properties.

2. Aprocess for improving the storage stability of fuel oil containing liquid components causing discoloration of the fuel oil and which form sediment during storage of the fuel oil, which comprises adding to the fuel oil from about 0.001% to about 5% by weight of an alkylated pyrrole, maintaining the oil in contact'with said alkylated pyrrole until sediment formation has occurred, and thereafter removing the resultant sediment from the oil.

3. The process of claim 2 further characterized in that said alkylated pyrrole is 2,5-dimethyl pyrrole.

References Cited in the file of this patent UNITED STATES PATENTS 

2. A PROCESS FOR IMPROVING THE STORAGE STABILITY OF FUEL OIL CONTAINING LIQUID CONPONENTS CAUSING DISCOLORATION OF THE FUEL OIL AND WHICH FORM SEDIMENT DURING STORAGE OF THE FUEL OIL, WHICH COMPRISES ADDING TO THE FUEL OIL FROM ABOUT 0.001% TO ABOUT 5% BY WEIGHT OF AN ALKYLATED PYRROLE, MAINTAINING THE OIL IN CONTACT WITH SAID ALKYLATED PYRROLE UNTIL SEDIMENT FORMATION HAS OCCURRED, AND THEREAFTER REMOVING THE RESULTANT SEDIMENT FROM THE OIL. 